JPH10153579A - Method and apparatus for analysis of sample - Google Patents

Abstract

PROBLEM TO BE SOLVED: To irradiate the surface of a sample with a laser beam with an irradiation intensity which is optimum for the gasification of a constituent substance even when the component and the composition of the substance are unknown and to analyze the substance under an optimum analytical condition, in a sample analytical method, in which a part to be analyzed on the surface of the sample is irradiated with the laser beam narrowed down to a very small diameter, in which the substance in the part is gasified and ionized, in which generated ions are put into a flying time type mass spectrometer, and in which the component and the composition of the substance are analyzed. SOLUTION: The irradiation intensity of a laser beam with which the surface of a sample 5 is irradiated can be selected (set and changed) arbitrarily by using a diaphragm 21 which is installed on the optical path of the irradiated laser beam or by using a transmittance- adjusting filter 23. When an unknown substance is analyzed, the sample is irradiated sequentially with the laser beam whose irradiation intensity is smaller. Thereby, the substance is analyzed by using analytical data obtained at a time when a part to be analyzed is gasified and and ionized under an optimum gasification condition. Thereby, the sample is not gasified so as to disappear when it is irradiated with the laser beam at an excessive irradiation intensity, and its mass can be analyzed with high accuracy because the analytical data obtained under an always optimum gasification and ionization condition is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sample analysis technique, and more particularly to a defect or a foreign substance present on a surface of a microstructure sample such as a semiconductor device, a mask reticle, a liquid crystal display, a memory disk, a circuit board, etc. The present invention relates to a sample analysis method suitable for use in the analysis of the composition and components of an unknown component substance such as a sample, and an apparatus for performing the method.

[0002]

2. Description of the Related Art First, the prior art will be described below by taking an analysis technique in the semiconductor industry as an example. In the production of semiconductors, it is essential to reduce defects in the manufacturing process in order to improve yield and reliability, and for that purpose, it is important to reduce foreign substances adhering to wafers during the manufacturing process. . This reduction of foreign matter adhering to the wafer generally involves identifying the foreign matter by inspection, observation, and analysis.
This is achieved by taking measures against foreign matter sources in the process apparatus and the process flow. In general, this inspection involves irradiating the wafer surface with laser light to detect its scattered light, or irradiating white light onto the wafer surface, capturing an image of the semiconductor circuit pattern, and performing comparative inspection. In addition, a method of detecting only foreign matter / defect is used.
Foreign matter and pattern defect portions detected in this way are:
More detailed observation can be performed with a scanning electron microscope or a high-resolution observation device. In addition, as a method of analyzing foreign matter / defects detected thereafter, an electron beam is used as a sample.
By irradiating (wafer) surface, a method of analyzing the characteristic X-rays emitted therefrom (XMA; X -ray M icro A nalysis) have been put into practical use, in particular, energy dispersive XMA are directed to inorganic Widely used for analysis. But,
In this XMA, it is difficult to analyze an organic substance, and it is difficult to control the depth of incidence of an electron beam into a sample. A method of irradiating a sample with a focus on the sample, vaporizing a constituent material at a portion to be analyzed on the sample surface, and analyzing molecules, atoms or ions thereof has been studied. Time-of-flight laser mass spectrometry is one of them. In this time-of-flight laser mass spectrometry, a sample is irradiated with a laser beam focused to a small diameter to vaporize constituent materials at a portion to be analyzed (small area), and ions generated by this vaporization are drawn out above the sample. This is an analysis method in which the time (flight time) required for the extracted ions to reach the detector is measured to determine the mass of the ions.

The time-of-flight laser mass spectrometry described above is
Conventionally, it has been mainly used for the analysis of organic substances, particularly biological compounds.However, since simultaneous analysis of multiple elements is possible, there is no influence of sample surface charging and the like, and the resolution of mass spectrometry is high, semiconductors and liquid crystals are analyzed. It is also effective for surface analysis, and various applications to that direction have been studied. As an example, Japanese Patent Application Laid-Open No. 63-146339 describes a time-of-flight laser mass spectrometer having a high-resolution observation function coaxially with a vaporizing laser beam. Also, Japanese Patent Application Laid-Open No. 6-194
No. 319 discloses that a laser beam for vaporization is squeezed finely to irradiate the sample surface, and ions or molecules generated by vaporization are generated.
A time-of-flight laser mass spectrometer and analysis method using a perforated objective lens (optical lens) and an Einzel lens (ion lens) for guiding atoms to a detector are described.

[0004]

SUMMARY OF THE INVENTION Among the above prior arts,
When analyzing a pattern defect or a foreign substance on a wafer surface in the process of manufacturing a microstructure semiconductor device by using the XMA analysis method, it is difficult to analyze an organic substance because the XMA analysis method is an elemental analysis method in principle. In addition, since the energy required to excite the foreign matter component varies depending on the element number, the energy is low for an element having a small element number called a light element, and is low for an element having a relatively large element number such as a metal. In some cases, it was necessary to irradiate high energy electron beams. The depth of penetration of the electron beam into the sample depends on the irradiation energy.If the irradiation energy of the electron beam is increased, the irradiation electron beam penetrates deeper into the sample, and defects and defects existing in the analysis location are detected. If the size of the foreign matter is small, the electron beam penetrates not only to the surface layer containing these defects and foreign matter components but also to the underlying layer,
Since many characteristic X-rays from the underlayer are generated and detected, it is difficult to analyze a minute surface area. In the method of irradiating a sample with a charged particle beam such as an electron beam or an ion beam, when the sample is an insulator, its surface is charged and drift of the irradiation beam is generated. Control was difficult.

Therefore, the inventors of the present invention configured to narrow down a laser beam and irradiate a sample to form a portion to be analyzed (small area) on the sample surface for the purpose of higher sensitivity and higher resolution analysis of a small area. The substance is vaporized, and the kinetic energy of the molecule, atom, or ion generated by this vaporization is calculated from the time required for the molecule, atom, or ion to fly in a vacuum and reach the detector. The analysis method for determining mass, that is, the application of time-of-flight laser mass spectrometry to the analysis of defects and foreign substances on a sample surface was examined in further detail.

First, in time-of-flight laser mass spectrometry,
Since the laser beam irradiates the sample surface, it is not affected by the charging of the sample surface as in the case of charged particle beam irradiation, so that there is no problem even if the sample is an insulator. However, in the time-of-flight laser mass spectrometry, a portion to be analyzed is vaporized, but the energy required for vaporization varies depending on the material and size of the portion to be analyzed. For this reason, it is necessary to optimize the energy of the irradiation laser beam for the analyzed portion every time the analysis is performed. In this regard, in the conventional analysis method, since the object to be analyzed is mainly a biological compound, the energy of the laser beam applied to the sample may be substantially constant, and fine energy adjustment has not been performed. However, when analyzing an unknown substance such as a substance constituting a defect or a foreign substance on the surface of a semiconductor device, it is not possible to know in advance the material or the like of a portion to be analyzed. It is not possible to analyze only the surface layer to be analyzed, so that even the underlying layer is vaporized, or conversely, the required surface layer to be analyzed is not vaporized even when irradiated with laser light. There was a problem that there was a case. In particular, the laser mass spectrometry method is based on the assumption that a required portion of the sample surface is vaporized, so that the energy setting of the irradiation laser beam is not appropriate, and particularly when the energy is too large, a desired analysis result is obtained. Not only is it impossible to obtain, but also because the portion to be analyzed vaporizes and disappears due to the laser beam irradiation at that time, there arises a problem that it becomes impossible to perform the analysis again.

[0007] Accordingly, an object of the present invention is to analyze analytes (defects and foreign substances) present at an analysis site on a sample surface layer by time-of-flight laser mass spectrometry. Even for unknown components, the irradiation conditions of the laser beam for irradiating the part to be analyzed can be set appropriately, so that the sample with high sensitivity and high resolution can be obtained without losing the part to be analyzed. An object of the present invention is to provide an analysis method and an analysis device capable of performing a surface analysis.

[0008]

In order to achieve the above object, in the sample analysis method of the present invention, when irradiating a sample with a laser beam, the energy of the irradiated laser beam is adjusted so that the analysis depth of the sample surface can be improved. It uses a method to adjust pod damage.

The first method is an analysis method for setting the energy of the irradiated laser beam according to the melting point of the material constituting the surface of the sample when the sample is irradiated with the laser beam. For example, in a semiconductor device manufacturing line, the materials used (surface constituent materials) are known, so the melting point corresponding to each material in advance and the irradiation laser light energy required to vaporize each material surface converted from it are calculated. Can be set and stored on a table (correspondence table). For example, the above table is prepared for silicon oxide, aluminum, tungsten, photoresist, and other materials as film forming materials on the surface of a semiconductor device. From this table,
The amount (volume or weight) of the surface portion that can be vaporized by one pulse laser beam irradiation can also be calculated. For this reason, if the constituent material of the surface of the sample to be analyzed is known, the analysis depth on the sample surface is set by setting the number of irradiations of the pulse laser light according to the surface constituent material based on the table. It becomes possible to control.

The second method is based on the irradiation condition setting table in the first method described above, or separately sets several stages of laser beam irradiation conditions in a fixed manner, and sequentially changes from weak energy to strong energy. This is a method of irradiating a laser beam while increasing the irradiation energy. When identifying a portion to be analyzed and irradiating the portion with a laser beam to vaporize the sample surface, when the constituent material of the sample surface is unknown, or an unknown substance attached to the sample surface (foreign matter, etc.) When performing analysis, it is difficult to preset irradiation energy appropriate for the analysis. Therefore, when the energy of the irradiation laser beam is larger than the required vaporization energy value of the analyzed portion, the laser beam is vaporized not only at the desired analyzed portion but also over a wide range including the vicinity thereof. When an area wider than the desired analysis location is vaporized, a large number of noise signals from areas other than the desired analysis area are mixed and detected, so that the analysis sensitivity for the desired analysis area is substantially reduced. For this reason,
The energy required to vaporize only that part (or
It is necessary to irradiate a laser beam having an energy less than that. In the present invention, by setting the energy of the irradiation laser light in several stages and irradiating the analysis target in ascending order of energy, the laser light irradiation with an energy larger than the required vaporization energy value only for the analysis target is performed. Can be prevented. In other words, the energy of the laser light applied to the analyzed portion is sequentially increased stepwise, and the increase in the energy of the irradiated laser light is stopped when the analyzed portion is vaporized and desired analysis data is obtained. Accordingly, it is possible to prevent vaporization of a sample surface region (for example, an underlayer) other than the analyzed portion.

[0011] In the sample analysis method of the present invention,
In addition to adjusting the energy of the laser beam applied to the sample surface, by cooling the sample, thermal diffusion on the sample surface when the laser beam is applied can be suppressed.
By suppressing the thermal diffusion due to the cooling of the sample, the volume of the sample surface region to be vaporized is reduced, and a smaller region can be analyzed.

Further, when the sample is irradiated with the laser beam by the first and second methods described above, if the desired analysis portion on the sample surface is not vaporized and disappeared by one pulse laser beam irradiation, By performing pulsed laser light irradiation a plurality of times, separately storing the analysis data obtained in each time, and adding the analysis data of each time, the influence of random noise is reduced, and the analysis at the desired analysis location is performed. Sensitivity can be improved. Further, when the analysis desired portion is the sample inner layer portion, the pulse laser beam irradiation is performed a plurality of times in the same manner as described above, the analysis data of each time is individually stored, and the analysis data of each time and the immediately preceding analysis data are respectively stored. By taking the difference from the analysis data at the time of analysis, it is possible to monitor the boundary surface (change point of the analysis data) between the layer desired to be analyzed and the layer above it, whereby the layer having the desired depth can be monitored. Analysis becomes possible.

The intensity (energy) of the above-mentioned irradiation laser light
The adjustment of, for example, in the middle of the optical path of the irradiation laser light, a plurality of aperture openings having different aperture diameters and a transmittance adjustment filter or the like adapted to the laser light wavelength are installed, and according to the desired irradiation laser light intensity. By setting a combination of these apertures and a transmittance adjusting filter, the above-described setting can be achieved. In addition, for cooling the sample described above, a cooling mechanism capable of controlling the temperature is attached to the sample holder, and according to the purpose,
This can be achieved by cooling the sample and controlling the cooling temperature. Furthermore, separately from the laser light for vaporizing the sample, the surface of the sample is irradiated with white light or the like, and an image of the surface of the sample is imaged with a TV camera or the like so that the portion irradiated with the laser light and its vicinity can be observed. With this configuration, at the time of analysis, first, an analysis location on the sample surface is specified using this observation function, and then the specified analysis location is irradiated with a laser beam for vaporization to analyze the analysis data. You can get it. It is desirable to add a mode switching function for switching the mode between the above-described mode for specifying the analyzed part and the mode for acquiring the analysis data. Furthermore, by observing the sample surface again after laser beam irradiation and analysis data acquisition, the intensity of the irradiated laser beam can be determined from the damage on the sample surface, the disappearance depth of the vaporized portion, etc. It is possible to determine whether to irradiate light.

As described above, in the surface analysis of a sample having an unknown composition, only a portion required for analysis can be analyzed with high sensitivity and high resolution. In addition, even if the sample is of an unknown composition, it does not happen that the analyzed part is lost without obtaining analysis data under appropriate analysis conditions, and the reliability and efficiency of analysis (inspection) are reduced. Can be improved.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to examples.

An embodiment of a method and an apparatus for analyzing a sample according to the present invention will be described with reference to FIGS. In a semiconductor device manufacturing process, a number of pattern forming steps are repeatedly performed. One pattern forming process generally includes steps such as film formation, resist coating, exposure, development, etching, resist removal, and cleaning. Through these steps, one circuit pattern is formed on the wafer. However, as shown in FIG. When 4 and the like occur, the semiconductor device becomes defective in operation, characteristics, and reliability. These foreign substances 1, projections 2, remaining patterns and residues 3, defective pattern shapes 4, and the like have different materials depending on the cause of occurrence (many of them are unknown materials) and also have various shapes and sizes. Therefore, as shown in FIG. 2, in the main pattern forming process, the appearance of the wafer is inspected to detect the presence or absence of foreign matter and defects for each wafer and each place, and their size and position coordinates. Then, in order to grasp the detailed contents of the foreign matter and the defect and to specify the cause and source of the foreign matter and the defect, a composition analysis of the substance constituting the foreign matter and the defective portion is performed. In the following, the analysis method and the analysis apparatus of the present invention will be described in detail by taking as an example the case of analyzing the material (component and composition) of a portion where such a foreign substance, defect, pattern residue or residue, pattern shape defect or the like has occurred. Will be described.

In the analyzing method and the analyzing apparatus according to the present invention, a required analysis point on the surface of the sample is irradiated with a narrowly focused laser beam to vaporize and ionize constituents such as foreign matter and defects existing at the required analysis point. Then, the ions generated by the vaporization and ionization are extracted from the sample surface, detected by a detector provided at a position sufficiently away from the sample surface, and the detected ion is generated at the generation position (analyzed location = laser beam). By measuring the time (flight time) required to reach the detector from the (irradiation position), the mass of the detected ions is obtained, and thus the constituents such as foreign matter and defects existing at the analysis site are determined. Analyzing (specifying components and compositions).

FIG. 3 shows a schematic configuration of an analyzer according to one embodiment of the present invention. The analyzer of this embodiment is roughly divided into
A sample chamber 7 including a sample stage 6, a laser light irradiation optical system for irradiating a laser beam for vaporizing the sample, an ion detection system for detecting ions emitted from the sample, and an observation device for observing the sample surface It comprises an optical system and a control unit 19 for controlling each unit of the apparatus. The sample 5 to be analyzed is placed on the sample stage 6, and the sample stage 6 is configured to be able to move to a desired position in accordance with a command from the control unit 19.
As a result, the sample (for example, a semiconductor wafer) 5 has an optical axis (Z Axis) in two directions (X, Y) in a plane (XY plane) perpendicular to
(Y direction). In addition, in order to bring the surface of the analyzed portion of the sample 5 to a predetermined position in the optical axis direction (Z direction) of the laser light irradiation optical system, the sample 5 is moved in accordance with a change in the thickness of the sample 5. It is configured to be able to move in any direction. The illustration of the sample stage drive mechanism for moving the sample is omitted.

A cooling unit 28 is provided on the sample table 6 to be in contact with the lower surface of the sample 5, and the cooling temperature is appropriately controlled by a command from the control unit 19 (or another arbitrary method). Thereby, the sample 5 can be cooled to an arbitrary temperature according to the purpose. The illustration of the sample cooling system is omitted.

The sample vaporizing laser light irradiation optical system includes a laser light source 20, an aperture 21, a lens 22, a transmittance adjusting filter 23, a mirror 10, an objective lens 9, and the like. The laser light source 20 outputs a pulsed laser light in response to a command from the control unit 19. The output laser light is supplied to a stop 21, a lens 22, a transmittance adjusting filter 23,
The light is irradiated onto the surface of the sample 5 to be analyzed via the optical path switching mirror 24, the light incident window 25, the mirror 10, and the objective lens 9. The aperture 21 and the transmittance adjusting filter 23 have a plurality of types of aperture diameters and transmittances, respectively.
One selected by a command from the control unit 19 is inserted and installed on the optical path of the irradiation laser light.

The ion detection system includes an ion extraction electrode 8, an ion deflector 11, an ion flight space 13, an ion reflector 12, an ion detector 14, an oscilloscope 15, and the like. The ions generated on the surface of the sample 5 by the irradiation of the sample vaporizing laser light are extracted by the ion extraction electrode 8, the orbit is corrected by the ion deflector 11, and then guided to the ion flight space 13. The ions that have flown in the ion flight space 13 are:
The light is reflected by the ion reflector 12, flies again in the ion flight space 13, enters the ion detector 14, and is detected there.

In the oscilloscope 15, the ion detector 1
4, the detection time of each ion detected every moment is measured, and the detection time of each ion is used to calculate the flight time of the ion (a pulse laser beam for sample vaporization is output from the laser light source 20). (The time from the point of time when each ion is detected until each ion is detected), and the result is sent to the data processing unit 16.

The data processing unit 16 obtains a relationship (time-of-flight spectrum) between the ion flight time and the detected ion amount from the transmitted time-of-flight data of each ion, and obtains a previously known ion flight time versus ion mass. This time-of-flight spectrum is converted into a mass spectrum according to the relationship with the number. From the mass spectrum obtained by this conversion, it is possible to determine the component / composition of the substance constituting the analyzed portion (= laser irradiation position) of the sample 5. The mass spectrum and various calculation results can be stored in the storage unit 17 and displayed on the display unit 18.

The observation optical system includes an observation illumination light source 26, an optical path switching mirror 24, and a TV camera 27. White light is emitted from the illumination light source 26, and is switched into the sample vaporization laser light via the optical path switching mirror 24 and is incident on the optical path of the sample vaporization laser light via the optical path switching mirror 24 according to the purpose.
The sample 5 is irradiated on a portion to be analyzed on the surface of the sample 5 in a coaxial relationship with the optical axis of the laser beam for sample evaporation. The reflected light from the surface of the sample 5 due to the irradiation of the observation illumination light is imaged by the TV camera 27, and the obtained video signal is transmitted to the display unit 18 via the control unit 19.
To display an image of the area around the analysis target on the sample surface.

Next, a method for analyzing foreign matter on the surface of a sample (semiconductor wafer) using the above-described analyzer will be described with reference to FIGS. FIG. 4 shows an analysis procedure in the analysis method of this embodiment. A sample (wafer) 5 in which the location of a foreign substance or a defect is determined by another inspection apparatus in advance is set in the loading section 29, and is loaded onto the sample table 6 in the sample chamber 7 from there. Then, by detecting a wafer shape such as an orientation flat or a notch of the wafer 5, or by detecting an alignment pattern formed on the wafer 5,
The position coordinates and the rotation state of the wafer 5 are corrected. Next, the position coordinates of the foreign matter obtained in advance by another inspection apparatus are stored in the control unit 1.
The sample table 6 is loaded onto the computer 9 and converted into coordinate values in accordance with the present analyzer, and the sample table 6 is moved so that the position of a foreign substance desired to be analyzed is just below the observation optical system. Position.

Next, the optical path of the laser light irradiation optical system is switched to the optical path of the observation optical system using the mirror 24, and the surface of the wafer 5 is illuminated with white light from the illumination light source 26, and the reflection from the surface of the wafer 5 is performed. Light is imaged by the TV camera 27. The captured image of the surface of the wafer 5 is displayed on the display unit 18.
While observing the image of the wafer surface,
(Position of the optical system in the optical path direction)
Focus the optics on the surface. Further, the focal position of this optical system is displayed on the monitor screen of the display unit 18 with a cursor or the like, and the position is precisely adjusted so that the analyzed portion (foreign matter position) comes there.

After the above-described position of the portion to be analyzed is completed, the mirror 24 switches the optical path of the optical system from observation to laser light irradiation. Next, in the control unit 19, a desired analysis condition is selected from a condition file in which a plurality of analysis conditions are set in advance, or the desired analysis condition is input to the control unit 19 according to a predetermined procedure. Set conditions. In accordance with the analysis conditions, the diaphragm 21 and the transmittance adjusting filter 23 installed in the optical path of the laser light irradiation optical system are changed and set. This analysis condition setting method will be described later in detail.

Next, in accordance with an analysis start command from the control unit 19, a laser beam for vaporizing the sample is pulse-oscillated from the laser light source 20, and is irradiated on the analyzed portion (foreign matter). here,
When the intensity of the irradiation laser beam has reached the energy required to vaporize the foreign substance to be analyzed, a part of the foreign substance to be analyzed is vaporized, and a part thereof is further ionized. It is detected at 14. The detection data is
Immediately through the oscilloscope 15, the data is transferred to the data processing unit 16, where calculations necessary for obtaining the mass spectrum of the foreign substance to be analyzed and the calculation results are stored, and the obtained mass spectrum and other calculation results are displayed on the display unit 18. An image is displayed on the monitor screen.

After that, the optical path of the optical system is switched again for observation by the mirror 24, and the image of the analyzed position, that is, the position irradiated with the laser beam is observed. As a result of the observation, if the foreign matter at the analyzed location has been vaporized and disappeared, the analysis at that location is completed. On the other hand, when the intensity of the irradiation laser beam is lower than the energy value required for vaporizing the foreign matter to be analyzed, the foreign matter to be analyzed still remains. Therefore, the analysis conditions are appropriately changed and set again according to the observation result, and the same part is analyzed again. Such a procedure is repeated to analyze the desired portion under the desired conditions. When the analysis of all the desired portions on the surface of the loaded sample wafer 5 is completed, the sample wafer 5 is transferred to the loading section 29. Unload.

As described above, the analysis method of the present invention has been described. However, as described above, in most cases, the material of foreign matter on the surface of a semiconductor wafer is unknown. Therefore, it is difficult to always irradiate the sample vaporizing laser beam under appropriate conditions (energy). For example, an organic substance such as a resist is vaporized at a relatively low energy, and a product formed by combining a fluorine gas or a chlorine gas with a metal is also vaporized at a low energy. However, a metal film or the like requires higher energy than these organic substances and fluorine / chlorine compounds, and silicon oxide and the like do not decompose, vaporize, or ionize unless further higher energy is given.

As a specific analysis example according to the analysis method of the present invention, a failure analysis example when a resist remains as a foreign substance on an Al pattern of a semiconductor wafer will be described. First,
After confirming the coincidence between the analyzed portion and the focal position of the laser light irradiation optical system by the method already described, the intensity of the irradiated laser light was set to 1 mJ, and the analyzed portion was irradiated with the laser light. As a result, it was found that not only the portion to be analyzed, but also the surrounding pattern was melted and vaporized over an area of several tens of μm. The spectrum obtained at this time was poor in time resolution and contained many signals of components considered to be those of the underlying substance. This is because the intensity (energy) of the irradiation laser beam is too high,
It was determined that the material in the surrounding area was also vaporized, and that the same component ions were not simultaneously generated from the same material due to the time delay of vaporization and ionization due to the thermal diffusion phenomenon. Is done. If the time resolution is poor, various component ions are mixed and detected within the same time, so that it is difficult to determine what the substance constituting the portion to be analyzed (foreign matter) is. In addition, vaporization of the region other than the analyzed portion itself increases the damage of the region around the analyzed portion. Furthermore, despite the inability to obtain an appropriate analysis result, the foreign matter at the location to be analyzed has completely disappeared due to vaporization, making it impossible to perform another analysis again.

Therefore, if the substance constituting the part to be analyzed (foreign substance) is unknown, a condition file including a plurality of laser beam irradiation conditions is set in advance, and the laser beam among the plurality of laser beam irradiation conditions is set. Irradiation was performed in order from the weakest irradiation intensity (energy). As described above, the irradiation energy of the laser light is variably set by changing the aperture diameter of the stop 21 provided in the middle of the irradiation light path or changing the transmittance of the transmittance adjusting filter 23. FIG. 5 shows an example of this condition file. Condition A corresponds to a proper energy condition for vaporizing an organic substance, and condition B corresponds to a proper energy condition for vaporizing a metal-fluorine / chlorine compound. Condition C is Al, condition D is W
Irradiation energy conditions corresponding to various materials are input to this condition file, as if they corresponded to the appropriate energy conditions for vaporizing the respective materials. Based on this condition file, a laser beam is irradiated to the analyzed portion in the order of the lowest irradiation energy, and each time, the analysis result (mass spectrum) is checked, and the analyzed portion (laser beam irradiated portion) is observed by the optical observation. The system is observed to determine the suitability of the analysis result (necessity of re-analysis) and the analysis depth. Then, when it is determined that the analyzed portion (foreign matter) is not properly vaporized and reanalysis is necessary, the reanalysis is performed by increasing the irradiation energy of the laser beam by one step. Through such a procedure, it is possible to surely obtain an appropriate analysis result before the foreign matter at the analyzed portion disappears.

In addition, when evaporating the portion to be analyzed,
Thermal diffusion on the (wafer) surface greatly affects the area of the region that is actually vaporized. FIG. 6 shows the outline. If the spread of heat on the sample surface is large, the region 30 to be vaporized also spreads as shown in FIG. Therefore, for example, if you want to analyze a small area,
The sample 5 is cooled using the sample cooling unit 28. In the above condition file, when irradiating a laser beam with a certain energy or more, the sample is cooled to reduce damage to the sample. The cooling means includes, for example, a method of cooling the cooling unit 28 with liquid nitrogen or the like, and the cooling is started by a command from the control unit 19 or a command by a manual switch before the analysis, injection of liquid nitrogen, or the like. As a result, as shown in (b) of the figure, the region 30 to be vaporized can be kept in a very small region, and at the same time, the time resolution can be prevented from decreasing as described above. Damage to the surface of the sample 5 can be reduced. In this way, by always setting appropriate analysis conditions for foreign substances and defects on the surface of the semiconductor wafer as a sample, the analysis results with high accuracy can be obtained.
(Spectrum) can be obtained.

As described above, in the analysis method of the present invention, a portion to be analyzed on the sample surface is vaporized. Therefore, by appropriately setting the laser beam irradiation conditions by the method described above, it is possible to obtain analysis data having different analysis depths every time pulse laser beam irradiation is performed. As an example, for the purpose of analyzing foreign matter 32 present inside the coating 31 provided on the sample surface, the sample surface is irradiated with pulsed laser light a plurality of times, and a mass spectrum is calculated from the analysis data of each time. FIG. 7 shows the results. In the first analysis, a spectrum including a peak 33 corresponding to Si and a peak 34 corresponding to SiO was obtained as shown in FIG. This is a component of the coating 31 itself in the outermost surface layer of the sample, as shown in FIG. In the second analysis, as shown in FIG.
The spectrum was similar to that of (a). Therefore, also in this case, as shown in FIG.
It turns out that it has not reached. Next, in the third analysis, as shown in FIG. 7C, a slight peak 33 corresponding to Si and a slight peak 34 corresponding to SiO were also detected, but separately correspond to W. A high peak 35 was detected. Therefore, in this case, it is determined that the vaporization of the sample reaches the foreign matter 32 and W, which is a component of the foreign matter 32 buried in the coating 31, is detected as shown in FIG. You. In this case, the difference between the spectra obtained in each analysis is taken to reveal the change point of the spectrum, so that the components of the coating 31 and the components of the foreign matter 32 can be discriminated. According to these methods, it is possible to accurately discriminate and acquire only the information on the target foreign substance 32 from the analysis results obtained when the same location on the sample surface is analyzed a plurality of times.

As a reference (sample standard), a portion having the same structure as the portion to be analyzed is set in advance, and a plurality of laser beam irradiations with different irradiation energies are performed on this reference portion in advance, and each time, By observing the analysis depth of the above, the analysis depth of the analysis results of each analysis of the location where a foreign substance, a defect or the like exists can be known from the result. Also, by taking the difference between the spectrum at the reference location and the spectrum at the foreign material location and comparing the peak positions, the effects of the pattern and coating components around the foreign material location can be grasped, and the components of the foreign material alone can be accurately discriminated. It becomes possible to acquire. In particular, when a foreign substance or defect to be analyzed is buried in the inner layer rather than in the outermost surface layer of the sample, not only the component of the foreign substance or defect but also the component of the upper layer is detected. However, according to the above method, the influence of the components in the upper layer can be easily eliminated, and the analysis depth of each analysis can be quantitatively grasped. As a result, it is possible to quantitatively specify the position and component of the foreign substance or defect to be analyzed in the depth direction.

As described above, the analysis method and the analysis apparatus according to the present invention have been described with reference to the typical embodiments. As is clear from the above, according to the present invention, the analysis conditions for unknown foreign substances and defects are determined. How to set, how to prevent heat diffusion on the sample surface to make the analysis space area of the analyzed area smaller, how to observe the analysis result and set the next analysis condition, and calculate the analysis result In addition, a method for accurately analyzing minute foreign matter and defects by a method of discriminating only data at an analysis point, and a typical configuration of an analyzer for performing these methods are provided. The present invention is also applied to the analysis of minute regions in fine structures such as masks and reticles other than semiconductor devices, liquid crystal displays, memory disks, circuit boards, and the like, as described in the initial application range. What you get. Further, the same applies to an analysis method and an analysis device that combine a plurality of features recited in the claims without departing from the scope of the present invention.

The typical effects obtained by the present invention are as follows:
The following is a brief description. A laser beam is applied to a portion to be analyzed (a minute foreign substance or a defect, etc.) on the surface of a sample (a fine circuit pattern or the like), and the portion to be analyzed is vaporized / ionized. Is measured, the mass number of the ions detected from the time of flight is determined, and in the analysis method and the analysis device for identifying the substance constituting the analyzed part, the intensity (energy) of the laser beam applied to the analyzed part is determined. ) Is set in a plurality of stages, and by irradiating the analyzed part in the order of weak irradiation energy, even if the substance constituting the analyzed part is an unknown substance, the analyzed part is damaged. Without disappearing or disappearing
Analysis can always be performed under appropriate analysis conditions.
In addition, by registering the above-described laser light irradiation conditions in a plurality of stages on the condition table in advance, analysis conditions can be set more efficiently. In addition, when the substance constituting the analyzed part is a known substance, the amount of vaporization of the analyzed part by laser light irradiation at each irradiation energy is obtained in advance, so that the irradiation energy of the laser light can be calculated. You can know the analysis depth. In addition, by observing the part to be analyzed immediately after the analysis and setting the next analysis condition based on the observation result, it becomes possible to execute the analysis with higher accuracy. Also,
By cooling the sample, thermal diffusion on the sample surface during laser light irradiation is suppressed, and only the laser light irradiation region can be vaporized, so that a more minute region can be analyzed. Furthermore, for each analysis result, by superimposing the obtained spectra or by taking the difference, it is possible to accurately discriminate and measure the component at the analyzed part and the surrounding components.

[0038]

As is clear from the above, according to the present invention, it is possible to set an appropriate analysis condition even when the constituent material at the analyzed part is unknown.
It is possible to perform highly accurate analysis on a wider variety of samples than before. At the same time, it is possible to analyze a finer area, and the accuracy of discriminating the analysis site from the surrounding substances is improved, so that highly sensitive and accurate sample analysis can be performed.

Therefore, the analysis method and the analysis apparatus method of the present invention are applied to a process for manufacturing a fine structure such as a semiconductor device, a mask, a reticle, a liquid crystal display, a memory disk, and a circuit board. When an unexpected defect or an unknown trouble occurs in the manufacturing process, a high-precision analysis can be immediately performed on the trouble and the cause of the trouble can be specified. Therefore, early and accurate measures can be taken, and a large number of defects can be prevented from occurring. As a result, problems such as defects and troubles in the process of manufacturing a microstructure can be reduced, and the manufacturing yield is improved. As a result, it is possible to improve the development efficiency when developing a new product and reduce the manufacturing cost when actually manufacturing the product. At the same time, pattern defects of various microstructures such as semiconductor devices can be reduced by the above effects, so that the reliability of the obtained product is improved.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing foreign matters, defects, and the like generated when forming a circuit pattern of a semiconductor device as an example of an analysis target by the analysis method of the present invention;

FIG. 2 is a diagram showing a process flow in a semiconductor device manufacturing process, which is an example of a target to which the analysis method of the present invention is applied;

FIG. 3 is a diagram showing one configuration example of an analyzer (laser-excited time-of-flight measuring mass spectrometer) according to the present invention;

FIG. 4 is a diagram showing an example of an analysis procedure of an analysis method (laser excitation time-of-flight measurement mass spectrometry) according to the present invention;

FIG. 5 is a diagram showing an example of a method for setting analysis conditions in the analysis method of the present invention;

FIG. 6 is a diagram for explaining a cooling effect of a sample in the analysis method of the present invention,

FIG. 7 is a diagram showing a calculation example of an analysis result in the analysis method of the present invention.

[Explanation of symbols]

1 ···· Foreign matter generated in semiconductor manufacturing process 2 ···· Projection defects generated in semiconductor manufacturing process 3 ··· Pattern residue and residue generated in semiconductor manufacturing process 4 Semiconductor Defective pattern shape generated in the manufacturing process, 5 ... Sample to be analyzed, 6 ... Sample stage, 7 ... Sample chamber, 8 ... Ion extraction electrode, 9 ... Objective lens , 10 ··· mirror, 11 ··· ion deflector, 12 ··· ion reflector, 13 ··· ion flight space, 14 ··· ion detector, 15 ··· oscilloscope, 16 Data processing unit 17 Storage unit 18 Display unit 19 Control unit 20 Laser light source 21 Aperture 22 ... Lens, 23 ... Excess ratio adjustment filter, 24… Optical path switching mirror, 25… Light entrance window, 26… Observation illumination light source, 27… TV camera, 28… Sample cooling unit 29, loading part, 30 area vaporized by laser beam irradiation, 31 coating film on the outermost surface of sample, foreign matter, 33 peak of Si, 34 ... SiO peak, 35 ... W peak.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Kinya Eguchi, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside Manufacturing Research Laboratory, Hitachi, Ltd. (72) Hiroyuki Yamaguchi 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Hitachi, Ltd. Production Technology Laboratory (72) Inventor Fumio Mizuno 882 Ma, Hitachinaka-shi, Ibaraki Pref. Hitachi, Ltd.Measurement Division

Claims (14)

[Claims] An object to be analyzed on a sample surface is irradiated with a laser beam focused to a small diameter to vaporize a substance constituting the object to be analyzed, and atoms, molecules or ions generated by the vaporization are detected. Then, in the sample analysis method for analyzing the substance constituting the analyzed part, the intensity of the laser light applied to the analyzed part is changed to analyze the analyzed part from the sample surface. A sample analysis method comprising controlling a depth and an amount to be analyzed. 2. The method according to claim 1, wherein the irradiation intensity of the laser light applied to the portion to be analyzed is changed by presetting a plurality of laser light irradiation intensities suitable for vaporizing each of a plurality of substances having different component compositions. 2. The sample analysis method according to claim 1, wherein the method is performed by selecting any one of the preset plurality of laser beam irradiation intensities. 3. The method according to claim 1, wherein the change in the irradiation intensity of the laser light irradiating the portion to be analyzed is performed in order from the lower irradiation intensity of the laser light to the higher irradiation intensity. Sample analysis method. 4. The method according to claim 1, wherein the selection of the laser beam irradiation intensity is sequentially performed from a predetermined one of the plurality of predetermined laser beam irradiation intensities in a direction from a lower intensity to a higher intensity. 3. The sample analysis method according to 2. 5. An object to be analyzed on a sample surface is irradiated with a laser beam focused to a small diameter to vaporize a substance constituting the object to be analyzed, and atoms, molecules or ions generated by the vaporization are detected. Then, in the sample analysis method for analyzing a substance constituting the analyzed part, the irradiation of the laser light to the analyzed part is performed while cooling the sample. 6. The sample analysis method according to claim 1, wherein the irradiation of the laser beam to the analyzed portion is performed while cooling the sample. 7. An object to be analyzed on a sample surface is irradiated with a laser beam focused to a small diameter to vaporize a substance constituting the object to be analyzed, and an atom, molecule or ion generated by the vaporization is detected. Then, in the sample analysis method for analyzing a substance constituting the analyzed part, the laser light applied to the analyzed part is pulsed laser light, and the pulsed laser light is applied to the analyzed part a plurality of times. Then, the atoms, molecules, or ions generated from the analyzed portion are separated and detected at each time of each of the plurality of pulsed laser beam irradiations, and the analyzed portion is configured at each time. A sample analysis method characterized by analyzing a substance. 8. The method according to claim 8, further comprising the step of comparing the analysis results obtained in each of the plurality of pulse laser beam irradiations to detect a change in a depth direction from the sample surface of the substance constituting the part to be analyzed. 8. The method of claim 7, wherein
The sample analysis method according to 1. 9. The method according to claim 8, wherein the laser light applied to the analyzed portion is pulsed laser light, and the pulsed laser light is applied to the analyzed portion a plurality of times. 7. The method according to claim 1, wherein the atoms, molecules, or ions generated from the site to be analyzed are separated and detected each time, and a substance constituting the site to be analyzed is analyzed each time. The sample analysis method according to any one of the above. 10. The method according to claim 1, further comprising the step of comparing the analysis results obtained each time of said plurality of pulsed laser beam irradiations to detect a change in a depth direction from a sample surface of a substance constituting said analyzed portion. The sample analysis method according to claim 9, comprising: 11. A laser beam means for irradiating a laser beam with a small diameter to a portion to be analyzed on a sample surface, an ion detecting device for detecting ions vaporized and generated from the portion to be analyzed by the laser beam irradiation, Time-of-flight measuring means for measuring the time of flight of the ions from the time of the irradiation of the laser light to the time of detection of the ions, and from the measured time of flight of the ions, Mass spectrometry means for performing mass spectrometry, wherein the laser light means is configured to irradiate the laser light for irradiating the analyzed portion with an irradiation intensity for changing the irradiation intensity according to an analysis purpose. A sample analyzer, further comprising a laser beam intensity adjusting means. 12. The irradiation laser light intensity changing means includes a variable aperture stop provided in the optical path of the irradiation laser light and a variable transmittance transmission light provided in the optical path of the irradiation laser light. The sample analyzer according to claim 11, comprising one or both of the rate adjustment filters. 13. A laser beam means for irradiating a laser beam focused to a minute diameter on a portion to be analyzed on a sample surface, an ion detecting device for detecting ions vaporized and generated from said portion to be analyzed by said laser beam irradiation, Time-of-flight measuring means for measuring the time of flight of the ions from the time of the irradiation of the laser light to the time of detection of the ions, and from the measured time of flight of the ions, Mass spectrometry means for performing mass spectrometry, comprising: a sample cooling device for irradiating the laser beam to the analyzed portion with the analyzed portion cooled to a low temperature. A sample analyzer, further comprising means. 14. The laser beam irradiating means irradiates the portion to be analyzed with a pulsed laser beam a plurality of times, and the mass analyzing means irradiates the pulsed laser beam a plurality of times. The sample analyzer according to any one of claims 11 to 13, wherein mass spectrometry of a substance constituting the analyzed portion is performed each time.